A radiative forcing analysis of tropical peatlands before and after their conversion to agricultural plantations

The tropical peat swamp forests of South‐East Asia are being rapidly converted to agricultural plantations of oil palm and Acacia creating a significant global “hot‐spot” for CO2 emissions. However, the effect of this major perturbation has yet to be quantified in terms of global warming potential (...

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Bibliographic Details
Published in:Global change biology 2018-11, Vol.24 (11), p.5518-5533
Main Authors: Dommain, René, Frolking, Steve, Jeltsch‐Thömmes, Aurich, Joos, Fortunat, Couwenberg, John, Glaser, Paul H.
Format: Article
Language:English
Subjects:
Acacia
Acacia plantation
Agriculture
Carbon
Carbon Cycle
Carbon dioxide
Carbon Dioxide - analysis
Carbon dioxide emissions
Carbon sequestration
Carbon sinks
Climate change
CO2 emissions
Conservation of Natural Resources
Conversion
Cooling
Cooling effects
Drainage
drainage‐based land use
Earth
Equivalence
Fluxes
Forests
Gases
Global Warming
global warming potential
Greenhouse effect
Greenhouse gases
Oil
oil palm plantation
Peat
Peatlands
Plantations
Radiation
Radiative forcing
Swamps
Tropical climate
Tropical forests
tropical peatland
Wetlands
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Summary:The tropical peat swamp forests of South‐East Asia are being rapidly converted to agricultural plantations of oil palm and Acacia creating a significant global “hot‐spot” for CO2 emissions. However, the effect of this major perturbation has yet to be quantified in terms of global warming potential (GWP) and the Earth's radiative budget. We used a GWP analysis and an impulse‐response model of radiative forcing to quantify the climate forcing of this shift from a long‐term carbon sink to a net source of greenhouse gases (CO2 and CH4). In the GWP analysis, five tropical peatlands were sinks in terms of their CO2 equivalent fluxes while they remained undisturbed. However, their drainage and conversion to oil palm and Acacia plantations produced a dramatic shift to very strong net CO2‐equivalent sources. The induced losses of peat carbon are ~20× greater than the natural CO2 sequestration rates. In contrast, a radiative forcing model indicates that the magnitude of this shift from a net cooling to warming effect is ultimately related to the size of an individual peatland's carbon pool. The continuous accumulation of carbon in pristine tropical peatlands produced a progressively negative radiative forcing (i.e., cooling) that ranged from −2.1 to −6.7 nW/m2 per hectare peatland by 2010 CE, referenced to zero at the time of peat initiation. Peatland conversion to plantations leads to an immediate shift from negative to positive trend in radiative forcing (i.e., warming). If drainage persists, peak warming ranges from +3.3 to +8.7 nW/m2 per hectare of drained peatland. More importantly, this net warming impact on the Earth's radiation budget will persist for centuries to millennia after all the peat has been oxidized to CO2. This previously unreported and undesirable impact on the Earth's radiative balance provides a scientific rationale for conserving tropical peatlands in their pristine state. Tropical peatlands in South‐East Asia store large amounts of carbon in their peat soils. Widespread conversion of tropical peatlands to agricultural oil palm and pulp plantations entails draining water from the peat soils. These drier soil conditions lead to peat carbon being rapidly released to the atmosphere as carbon dioxide. We calculated the effect of these significant greenhouse gas emissions on the global climate and found that they will contribute to climate warming for several centuries. Reducing drainage of tropical peatlands and restoring drained peatlands will r
ISSN:1354-1013
1365-2486
DOI:10.1111/gcb.14400